Independent Swiss master watchmaker Andreas Strehler has developed a new movement which combines his Remontoir d’égalité (constant force) with a Tourbillon.
In Andreas Strehler watches, the energy for operating the movement is stored in twin mainspring barrels. The running down of the two mainsprings is limited by an epicyclical gear. Only the optimal part of each mainspring is used where the power supplied is practically constant.
Even by using the highest-grade lubricants and the tightest tolerances in manufacturing each component, the flow of energy from the mainsprings will be subject to variations. Changes in temperature or in the position of the watch will cause such variations. To filter these variations, Andreas Strehler employs a Remontoir d’égalité or constant force escapement.
In Andres Strehler’s Remontoir d’égalité,t he energy supplied from the twin mainspring barrels through the gear train is accumulated in a spring, acting on a satellite arm held in position by the star wheel (the satellite). One tooth of this star wheel is resting on the palette-stone of the palette arm.
This palette arm constantly moves ahead. Every second, the palette arm releases the star wheel. The star wheel turns by one tooth and the satellite arm jumps ahead by 6°. The satellite wheel then rests again against the palette-stone and the cycle starts anew.
When moving ahead by 6°, the satellite arm recharges the spring which drives the escapement. The amount of energy transferred to the escapement thus is always the same, it is constant. The energy is transferred to the escapement through an axis.
The escapement mounted on this axis is a Tourbillon. The Tourbillon is a special escapement. It is also one of the most complicated components known to watchmaking. In a Tourbillon, the whole escapement including the balance rotates typically once a minute.
The idea behind the Tourbillon is that the balance, despite its name, is never perfectly balanced. This means that it oscillates slightly differently, depending on its position in space.
When the Tourbillon was invented by Abraham Louis Breguet in 1801, men wore pocket watches. A pocket watch is carried vertically, and the balance always oscillates on a horizontal axis. This means that gravity pulls more on any part of the balance which is thicker or heavier. Now, by rotating the whole escapement and hence the balance once a minute, it did not matter if the balance was slightly imperfect: Gravity would still pull heavier on the thicker part of the balance. But, by its rotation, this effect would even itself out. The balance would, for one part of the rotation of the Tourbillon, work uphill, so to speak. But for the other part of the rotation of the Tourbillon, it would work downhill (and for the rest of the time in neutral).
In his quest for perfection, Andreas Strehler has designed, constructed and built a movement where internal influences on the already pretty linear power supply from the epicyclically limited twin mainspring barrels is filtered through a Remontoir d’égalité and transferred to a Tourbillon escapement mounted on the same axis to eliminate the influence of gravity on the escapement.
The Trans-axial® Remontoir Tourbillon escapement is hand wound, using Andreas Strehler’s own true conical gear wheels (which are the envy of the watch industry). To show the power left in the two mainspring barrels, the movement has a power reserve indication using an extremely small differential gear, another speciality of Andreas Strehler.
The Remontoir d’égalitéis mounted on three roller bearings and powers a separate jumping seconds indication. The Tourbillon is held in position by two gold chatons.
Trans-axial Remontoir Tourbillon
Impulse: Double main spring barrel, energy regulated by a remontoir d’égalité
Plates and bridges: Three 18k gold bridges, Central Main Plate and bridges are decorated to the highest standards, edges bevelled and polished by hand, fully decorated movement
Escapement: swiss lever escapement designed by Andreas Strehler
Regulating system: Free-Sprung balance with Breguet overcoil and eight adjustment screws
Frequency: 3 Hz / 21’600 A/h
Number of jewels: 37, 3 gold chatons
Number of individual parts: 250
Size: 32.0 x 30.0 mm
Height: 7.01 mm (without Tourbillon)
Power reserve: 78 h, limited by a differential stop works
Functions: Hour, minute, small jumping second, constant force, Tourbillon, power reserve indication (micro differential gear train)
Winding-mechanism: Hand winding with conical gear wheels
Speciality: Constant force Tourbillon, Remontoir trans-axial underneath the Tourbillon, special roller bearing for the remontoir.